The present invention relates to low cost C-frame motors and their methods of manufacture, and more particularly, to new and improved twin bobbin C-frame motors and their methods of manufacture.
conventional C-frame motor construction, a first stack of magnetically conductive laminations is provided with aligned circular-shaped rotor openings at one end and aligned U-shaped openings at a second end. A separate elongated second stack of laminations is mounted the first stack of laminations across the aligned U-shaped openings of the first stack of laminations after a single electrically conductive coil is positioned over the separate elongated second stack of laminations. The second stack of laminations thus provides a coil winding area about which an electrically conductive coil can be positioned for introducing flux into a rotor that is received within the aligned rotor openings of the first stack of laminations, in order to provide a magnetic inductor circuit.
In such conventional C-frame motors, the outer cross sectional shape of the coil winding area of the second stack of laminations is typically square when the stack height of the motor equals the width of the coil winding area cross section. This is the most efficient stack height with respect to copper usage in the electrically conductive coil because the ratio of the perimeter to the cross sectional area of the coil winding area is at a minimum. As the stack height of the laminations is increased, to increase the horsepower output of the motor, the cross sectional area to the coil winding area becomes more and more rectangular and the ratio of the perimeter to the area of the winding area becomes larger and less efficient. Also, reducing the stack height to make lower horsepower output motors causes the cross sectional area of the coil winding area to become more rectangular and therefore, also less efficient. The legs in the first stack of laminations and the second stack of laminations that form the coil winding area typically have approximately equal cross sectional areas.
As disclosed in my aforementioned copending patent application U.S. Ser. No. 08/199,600 entitled LOW COST C-FRAME MOTORS AND METHODS OF MANUFACTURE, it has been discovered that if the outer cross sectional shape of the coil winding area in the second stack of laminations is provided with a generally circular outer cross sectional configuration which is actual to the area in the legs of the first stack of laminations, the motor will always have a minimum ratio of winding area meter to cross sectional area and therefore the minimum amount of usage of copper. In some intances, more lamination material is required, and in other cases, less lamination material is required. However, in all instances, the copper savings are more than sufficient in order to provide significant overall savings as long as the coil winding area of the second stack of laminations has a generally circular construction.
In addition to the new and improved design for C-frame motors as disclosed in my aforementioned copending patent application, it has also been discovered that both of the spaced side legs of the first stack of laminations can he usefully employed for coil winding purposes, whether made in the typical four-sided (square or rectangular) shape or in a higher order (greater than four sides up to a partial or full circular) shape. In either such case, if the coil winding areas the spaced side legs in the first stack of laminations are positioned in proximity to the aligned openings and rotor, several important advantages can be achieved. This construction permits electrically conductive coils to be mounted over the spaced side legs, thus providing a greater and/or more efficient flow of magnetic flux through the rotor of the magnetic inductor circuit. Also, the electrically conductive wire forming the electrically conductive coil that is positioned over each of the spaced side legs has less than one-half the length of a single electrically conductive coil in a conventional C-frame motor construction, and the diameter of the electrically conductive wire can be reduced, as well.
The use of less than one-half the length for the electrically conductive coil mounted on each pair of spaced side legs of the first stack of laminations is due to the greater winding length smaller mean winding diameter for the two electrically conductive coils positioned on the spaced side legs as compared to a single electrically conductive coil in a conventional C-frame motor construction. As a result, there is a shorter wire length for each of the electrically conductive coils that are positioned over one of the spaced side legs. Additionally, there is a reduction in the diameter of the electrically conductive wire for both electrically conductive coils. This wire diameter reduction is believed due to the shorter wire length of each electrically conductive coil, the greater winding surface area of the two electrically conductive coils and the proximate location of the spaced electrically conductive coils on the surfaced side legs of the first stack of laminations relative to the aligned rotor openings and rotor.
The aforementioned proximate location of the electrically conductive coils provides a efficient flow of magnetic flux from the magnetic inductor circuit through the poles and into the rotor of the motor. In some instances, the overall dimension of the motor can be reduced also reduce the length of the flux path, as well. In fact, performance tests have established that motors constructed with this construction have a greater overall efficiency than conventional C-frame motors of the type described above. For example, this improved motor efficiency was established where the outer cross sectional side leg shape had a higher order greater than four sides, along with savings in copper usage. However, this improved motor efficiency is also possible even where the outer cross sectional configuration of the side legs have the typical four-sided (square or rectangular) configuration.
In the discussion that follows, the present invention discloses new and improved motor constructions of the type generally described above, as well as new and improved methods of manufacturing such motor constructions also with improved efficiency and lower material usage.